Hysterectomy (surgical removal of the uterus) is performed on approximately 600,000 women annually in the United States. For approximately 340,000 women, hysterectomy is probably the best current therapeutic choice for the treatment of their diseases (uterine cancer, endometriosis, menorrhagia, and prolapse). For approximately 60,000 women with dysfunctional uterine bleeding (abnormal menstrual bleeding that has no discrete anatomic explanation such as a tumor or growth), newer endometrial ablation techniques may be an alternative to hysterectomy. For approximately 200,000 women with benign but symptomatic (excessive bleeding, pain, and “bulk” sensations) muscular tumors of the uterus, known as leiomyoma or fibroids, newer treatment methods have been developed which may spare these women a hysterectomy, as well.
Hysterectomy for treating uterine fibroid disorders, though effective, has many undesirable characteristics. Thus, any method which can approximate the therapeutic result of a hysterectomy without removing the uterus (and commonly the ovaries since they are closely adjacent to the uterus) would be a significant improvement in this field.
The undesirable characteristics of hysterectomy include a known mortality rate of 0.5 deaths per 1000 hysterectomies. Stated another way, the risk of death within 30 days of hysterectomy is thirty times greater for women who have had a hysterectomy than for women of similar ages and backgrounds who have not had a hysterectomy. Morbidity (medical symptoms and problems short of death) associated with hysterectomy include possible injury to adjacent organs (the bladder, the ureters, and bowel), hospital stay of approximately one week, five to six weeks of slow recovery to normal activity, three weeks of absence from work, direct medical expenses of at least $10,000, indirect cost of time away from work, a future three-fold increase in the incidence of cardiovascular disease, decreased sexual pleasure in approximately thirty percent of women, and depression and anxiety for many years after the hysterectomy for approximately eight percent of women.
The endometrium is a glandular mucous membrane of the uterus, the thickness and structure of which varies with the phase of the menstrual lining. It is normal for portions of the lining to slough off and bleed during menstruation, but many women suffer from painful dysfunctional uterine bleeding or endometritis. Thus, endometrial ablation (removal or destruction of the endometrium) may be an alternative to hysterectomy for approximately 60,000 women. A great many new devices have been invented to perform endometrial ablation to treat dysfunctional uterine bleeding. To distinguish the present invention and its applications from endometrial ablation devices, the endometrial ablation devices will be briefly described. Endometrial devices can be categorized into two major groups: devices which require direct visualization of the endometrium to apply an energy source to ablate the endometrium; and those that do not require visualization for their application.
Direct visualization of the lining of the uterus is accomplished by placing a hysteroscope through the vagina and into the uterus via the cervical os (opening). The hysteroscope image is then displayed as a color image on a TV monitor adjacent to the patient. The gynecologist then manipulates the hysteroscope and endometrial ablation instrument to ablate the lining of the uterus. Endometrial lining ablation instruments directed by hysteroscope include radio frequency or electrosurgery loops, roller-balls, and lasers. The goal of all of these hysteroscopic endometrial ablation instruments is to transfer heat energy to the endometrium sufficiently to heat and thereby destroy it. An ablated endometrium cannot respond physiologically or pathologically to hormonal stimulation and cannot, therefore, proliferate and bleed.
To treat all of the endometrium, it must be entirely visible through the hysteroscope. However, visualization of all of the endometrium is difficult. The uterus must be distended like a water balloon to allow adequate visualization. In this distension process, some women become water intoxicated and hyponatremic. Furthermore, the uterine cavity is an awkward shape, somewhat triangular and often angulated. Directly visualizing each and every square millimeter of endometrial surface and ablating each and every square millimeter is seldom achieved. Consequently, portions of the dysfunctional endometrium may persist and dysfunctional bleeding may continue.
Because of these hysteroscopic visualization and ablation limitations, alternative methods have been invented to destroy the lining of the uterus without the need at all for visualization of the uterine lining. On such method uses a prototypic instrument, the ThermaChoice™ balloon, which is produced by GyneCare, a division of Ethicon, Inc. (see U.S. Pat. No. 5,776,129, incorporated in its entirety herein). This device is inserted through the vagina into the uterus via the cervical os. The balloon is shaped like a triangle to conform to the shape of the uterus. Once in place, hot fluid is added to the balloon to heat and destroy the uterine lining. Treatment only occurs where the balloon is in adequate contact with the uterine lining. As an alternative, hot fluids can be directly introduced into the uterus (e.g., ENABL brand system manufactured by Innerdyne, Inc., and marketed by U.S. Surgical Corporation).
Endometrial destruction can also be brought about with chemical damage, photochemical injury, or thermal damage (heat or cold). Energy that reaches and destroys the cells of the endometrial lining of the uterus potentially destroys the uterine lining and thereby treats dysfunctional uterine bleeding.
Surgically removing fibroids or in situ ablation of uterine fibroids is a bit like eradicating ants in the pantry—they are not all seen from one perspective and there may be a lot of them. Commonly, a diagnosis of uterine fibroids involves the presence of multiple fibroids, often averaging ten fibroids or more per afflicted uterus. Consequently, it is difficult to know which fibroid is causing symptoms to the patient (bleeding, pain, and bulk effects on adjacent organs). Furthermore, fibroids occur at different layers in the uterus. Uterine fibroids can occur adjacent to the lining of the uterus (submucosal fibroid), in the myometrium (intramural fibroid), or adjacent to the outer layer of the uterus (subserosal fibroid). Consequently, if one is directly observing the uterus from the peritoneal cavity, only subserosal fibroids would be seen. If one is directly observing the uterus from the endometrial surface of the uterus, only the submucosal would be seen. Fibroids deep within the wall of the uterus are poorly visualized from either surface. Finally, since fibroids come in all sizes, only the larger fibroids will be seen in any case.
Clearly, the strategy of identifying which individual fibroid is causing symptoms (when there are often many), finding that fibroid, and then either removing or destroying that individual fibroid is a rather complex strategy. It is therefore easy to understand why the hysterectomy is such a common surgical choice. With hysterectomy, all uterine fibroids are removed in one stroke.
In 1995, it was demonstrated that fibroids, in a uterus that contained one or multiple fibroids, could be treated without hysterectomy using a non-surgical therapy, specifically comprising bilateral intraluminal occlusion of the uterine arteries (Ravina et al., “Arterial Embolization to Treat Uterine Myomata”, Lancet Sep. 9, 1995; Vol. 346; pp. 671–672, incorporated in its entirety herein). This technique is known as “uterine artery embolization”. The technique uses standard interventional radiology angiographic techniques and equipment, whereby the uterine arteries are accessed via a transvascular route from a common femoral artery into the left and right uterine arteries.
Three facts explain the success of uterine artery embolization. First, it has been established that pelvic bleeding from a wide variety of sources (e.g., auto accidents, surgical errors, and post partum hemorrhage) can be effectively controlled with embolization techniques using coils placed in arterial and venous lumens (U.S. Pat. Nos. 4,994,069, 5,226,911, and 5,549,824, all of which are incorporated in their entireties herein) (available from Target Therapeutics), or particles (GELFOAM pledgets, available from Upjohn, Kalamazoo, Mich., or IVALON particles, available from Boston Scientific).
Second, fibroids live a tenuous vascular life with very little ability to recruit a new blood supply from the host when the primary blood supply is compromised. Third, the uterus has a dual (or redundant) blood supply, the primary blood supply being from the bilateral uterine arteries, and the secondary blood supply from the bilateral ovarian arteries.
Consequently, when both uterine arteries are occluded, i.e. bilateral vessel occlusion, the uterus and the fibroids contained within the uterus are both deprived of their blood supply. However, as demonstrated by Ravina et al., the effect on the fibroid is greater than the effect on the uterus. In most instances, the fibroid withers and ceases to cause clinical symptoms.
The uterine artery embolization technique utilized by Ravina et al. uses standard transvascular equipment, available in typical interventional radiology angiography suite. This equipment includes guide catheters to selectively enter the tortuous right and left uterine arteries, Ivalon or Gelfoam particles, and intravascular coils. With skill and these standard angiographic tools, the uterine arteries can be occluded bilaterally and fibroid disease treated through a 2 mm hole in the right groin and through the right common femoral artery. Following the procedure, the arterial puncture site is held with manual pressure for fifteen minutes. While post-procedural pain is often significant, and requires intravenously delivered pain medication, the patient is typically fully recovered in a few days.
One problem with present methods of uterine artery embolization is that many physicians do not possess the skill or equipment necessary to perform catheter-based uterine artery embolization under radiologic direction. Accordingly, only hundreds of uterine artery embolizations have been performed, worldwide, over the past three years, whereas hundreds of thousands of hysterectomies have been performed each year for uterine fibroids which are symptomatic.
What is needed, therefore, are devices and methods to occlude arteries such as the uterine arteries.